Stroke, the leading cause of adult disability in the US and the fourth leading cause of death, has a higher incidence in minority populations. More than half of ischemic stroke patients have sleep apnea, a very common and important predictor of poor stroke outcomes including death and physical disability. Reasons for this high prevalence are poorly understood, and treatment of sleep apnea is a particular challenge in the stroke population due to poor compliance with existing treatments. A better understanding of the pathophysiology of post-stroke sleep apnea could yield new, more tolerable targets for treatment. Daytime fluid pooling in the legs may be redistributed at night into more rostral compartments. Through pharyngeal narrowing and increased airway collapsibility, these fluid shifts have been shown to contribute to sleep apnea in some populations. Nocturnal rostral fluid shifts have not been investigated in stroke patients, where impaired mobility and iatrogenic fluid overload are common. The parent study for this project, the Brain Attack Surveillance in Corpus Christi Sleep Apnea (BASIC) project, is an ongoing population-based stroke surveillance study that identifies all stroke cases in Nueces County, Texas. This project has made many important discoveries about stroke in Hispanics, the largest minority group in the US, and non-Hispanic whites, and its related study (BASIC-Sleep Apnea Project (BASIC-S)) is beginning to yield valuable new insights into the epidemiology of post-stroke sleep apnea. BASIC will continue to identify all ischemic strokes in Nueces County and will provide detailed baseline information while BASIC-S will provide sleep apnea testing with a validated portable cardiopulmonary test for part of the study period. In the current application, we add ancillary studies to the BASIC project including neck and leg circumference and bioimpedance spectroscopy measurements in the acute stroke period. We propose to relate these measures to the baseline post-stroke sleep apnea assessments and stroke outcomes. Given that recruitment is currently underway and will cease May 31, 2018, it is critical to begin the new assessments as soon as possible to maximize the sample size and power for the given study objectives. This ancillary study will allow us to answer important, novel questions about the pathophysiology of sleep apnea post-stroke within a bi-ethnic community in a cost-containing fashion, as we will use existing infrastructure for case identification and sleep apnea assessment. Recognition of nocturnal rostral fluid shifts will suggest targets for simple, tolerable treatments to ameliorate an important and common disorder, sleep apnea, in a devastating disease, stroke, in the largest and fastest growing US minority population.